[PD-dev] Connecting up an SQL Database to PD

[Mike McGonagle]

Hello all,

It has been several months since I first inquired about this idea, and
it seems there are some out there who think this would be a good idea.
So, in the interest of figuring out just how this could work with PD,
I would like to start a discussion about what sort of interface
objects should be created.

1.0 What the objects would look like.
My first thought is to design them so they operate like other already
existing PD objects. While there may not be a perfect match with other
objects, I am thinking more along the lines of what commands they
recognize and their basic functionality.

While I don't have a specific idea for how to implement these
connecting objects, I think that there would be three (or more)
different PD objects instantiated to work with a database. One object
to handle the connectivity, one object to handle the querying, and a
third to handle any results coming from a query.

A. While there could be multiple connectivity objects, each one would
point to a different database. This could be used to construct several
data paths, and each connectivity object would be passed a symbol to
use as a name for its data path. This name would then also have to be
passed onto each query and results object to link them to a particular
data path. (Does this need more explaination?)

B. There could be more than one query object, each one handling a
different query type (as PD doesn't really support strings, it might
be difficult to build a whole SQL statement using commands via an
inlet).

C. There could also be multiple result object, each "listening" for a
different parameter set.

2.0 Data Types, SQL, and PD
So far, the biggest hurdle that I see with this is Data Types. As PD
doesn't have much support for strings, there would either have to be
special handling involved, or we just agree that a string in this
context would be a PD symbol. Also, all the other datatypes (with the
possible exception of a BLOB) would not really have a PD equivelent.
But then again, how might binary data be stored to a BLOB from within
PD?

3.0 Linking data into PD
Another idea for connecting the data from the database into a PD
patch, would be to map each of the fields in the database table to a
particular PD variable. While this might allow for increased
interaction, it would eliminate the use of any symbols returned from
the database.

4.0 Version 0.0
As this is still in this design stage, there are some things that I
would like to put off dealing with until there is a working set of PD
objects.

A. Currently works with one database. As there are so many different
types of databases out there, and most of them require additional
components to setup and configure, I would like to keep this as simple
as possible. Currently my idea is to use ONLY SQLite, as a backend.
This would be compiled directly into the PD external, as the SQLite
code implements a full SQL database in a single source file, it is
pretty easy to link this up directly without any other programs to
install.

B. All databases need to be designed externally. This means that no
CREATE TABLE functions or other commands that would manipulate the
database schema. This might be a problem is you need to create tables
on the fly, but I would think that we could get a good start on the PD
interface, and then take this idea up later.

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So, if any of you have any ideas on this topic, please feel free to
jump in and add your $0.02. It would be very much appreciated.

Thanks,

Mike